With the migration from analog to digital video surveillance continuing there remains a crucial requirement for reliable transmission of the video signal during today's period of coexistence when a company is using both analog and digital side-by-side. With many legacy installations, it has been coaxial cable handling images from a camera to monitoring or recording, or both.
Coax has its limitations, however: restricted transmission distance, signal degradation over long cable runs and interference, to name a few. This latter problem cannot be underestimated. For instance, a steel works using an electric arc furnace will quickly discover that the magnetic interference from the furnace prevents any copper based solution from working reliably, no matter how much shielding is used. In addition, networking, digital and Internet Protocol (IP) have ushered in Cat 5/Unshielded Twisted Pair (UTP) cable and high-speed Ethernet, employing IP to carry the digitalized video images. In some installations, wireless transmission - radio frequency, microwave, Wifi and mesh nets - play a role. Even then, most enterprise security video designs are not totally wireless. The technology is typically applied only to meet certain geographic or operational challenges.
The Light Solution
Then there is fiber optic cabling with its interference immunity, which solves the problem of magnetic interference at the afore-mentioned steel manufacturer. It also provides better inherent security, robust cabling distances and huge bandwidth capability. Fiber optic technology, a method of sending and receiving information over great distances using light as the carrier, boasts significant advantages, whether as a backbone or a total transmission solution. Among the advantages of fiber optics are better quality transmission; no interference from lightning strikes, short circuits, crosstalk, EMI or RFI; no interference from the high voltages used in fluorescent lights, card access door strikes and outdoor lighting systems. Fiber optic routes are also lightweight, stable within a wide temperature range, have a long service life, are more secure - i.e.
they are not easily tapped into or interfered with - and they have an extremely high bandwidth. This last characteristic is important when one considers that ongoing developments will continue to increase the amount of data transmitted.
Fiber as a prime security tool opens the applications doorway extraordinarily wide. There are almost unlimited capabilities of security video transmission and pan/tilt/zoom controls. For example, a single fiber strand deals with bi-directional signaling, so one fiber between two points can carry multiple streams of security video in one direction while pan/tilt/zoom control can go in the opposite direction, all simultaneously.
Additionally, fiber is superior to copper cabling in all performance measures. There is noticeable return on investment in cabling distances with inexpensive fiber. Scores of cameras can transmit their signals over only one or two fiber strands.
Whatever the mode, fiber wins over Cat 5/UTP. The bandwidth capacity of a single strand of standard multimode fiber is more than 45 times that of a Cat5 cable, while the maximum bandwidth capacity of single-mode fiber has yet to be reached, according to fiber optics experts. So, even though IP-based video is gaining users, there remains a serious distance limitation with UTP cabling infrastructure, hindering placement of cameras.
For example, using Cat 5/UTP, if a camera is located 1,000 feet from the head-end without any active signal conditioning, about 37% of the information will be lost in transmission, not counting the need and cost for signal amplification, ground fault correction and surge protection. Meanwhile, fiber optic devices can move images up to two miles from end to end on multimode fiber, while high-bandwidth single-mode fiber can carry signals up to 60 miles before regeneration of the signal is needed.
The Physical Properties of Fiber
Fiber optic cabling comes in two basic types: multimode and single-mode. Multimode fiber has a core size of either 62.5 or 50 microns and is commonly found providing connections between telecommunications closets within a building or campus. Preferred for most physical security applications, multimode uses low-cost LEDs or inexpensive lasers for transmission. It's easier to terminate and test. The multimode drawback: It has a distance limitation - usually out to three miles. Single-mode fiber, with a core size of 7 to 10 microns, typically handles longer distances of more than 50 miles in high bandwidth applications.
Fiber within most buildings is multimode. Some infrastructures have a combination of multimode and single-mode. No matter the mode, there needs to be a way to convert the video signal over to an optical format and back again. As a result, there are devices which are part of a fiber optics transmission system, such as receivers and transmitters, which can be combined into transceivers and video to fiber converters, connectors and adapters. Fiber connectors, for instance, come in several common styles, such as ST (round), SC (square) and LC (also square). This comes into play when realizing that devices for interfacing physical security equipment to fiber optic links can usually be ordered with either the ST or SC connector. Various adapters convert connections, such as connecting an ST video fiber encoder to an SC connector on a network fiber patch panel.
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